CHEM 200/202. Professor Gregory P. Holland Office: GMCS-213C. All s are to be sent to:

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1 CHEM 200/202 Professor Gregory P. Holland Office: GMCS-213C All s are to be sent to: My office hours will be held in GMCS-212 on Monday from 12 pm to 2:00 pm or by appointment.

ONLINE TOOLS Blackboard: one section for each lab. Links on sidebar to various resources: OWL - online homework and quizzes http:// www.cengage.

2 ONLINE TOOLS Blackboard: one section for each lab. Links on sidebar to various resources: OWL - online homework and quizzes Get OWL setup ASAP - OWL assistance can be found outside bookstore this week only (look for Cengage tent) ebook - a pdf version of the book openstaxcollege.org/details/chemistry New website this year: sdsuchem200.com

3 ANNOUNCEMENTS Waitlisters: Be sure to if you got in Recorded lectures (old lectures posted, scroll down) HW 3 & 4 due September 21 st (Chapter 3 & 4) Quiz 1 is due September 20 th (10 exam questions, timed 1 hr) Exam 1 is September 22 nd at 2 PM (Room Assignments to come) Note: OWL Assignments are due by 11:55 PM on due date

4 SUPPLEMENTAL INSTRUCTION Occur 15 times a week. Free to access, no reporting to faculty. Link to the SI schedule is on blackboard.

5 LECTURE OBJECTIVES Chapter 4.1 Writing and Balancing Chemical Equations. Write and balance chemical equations in molecular, total ionic and net ionic formats. Chapter Classifying Chemical Reactions & Stochiometry. Define 3 types of chemical reactions (precipitation, acid-base, oxidationreduction). Predict solubility of common inorganic compounds by using solubility rules Acid-base reactions and titration (neutralization). Compute the oxidation states for elements in compounds.

6 EXAM ROOM (1-3) FALL 2018 ROOM ASSIGNMENTS EXAMS 1 3 GMCS-333 AL-201 Lab TA: Section: Lab TA: Section: Chem Chem Chem Tranvo Chem Schroeder Chem Chem Chem Chem Chem Johnson Chem Chem Chem Chem Chem Xu Chem Chem ENS-280 SHW-012 Lab TA: Section: Lab TA: Section: Trammel Chem Chem Chem Younan Chem Chem Chem Sun Zhu Chem Chem Lin Chem Chem Chem Chem Bowles Chem Chem Chem Chem Yazdani Chem Chem Li Chem Chem

7 REACTION CLASSIFICATIONS There are three principle aqueous chemical reactions that we will focus on in this course: Precipitation reactions Acid-Base reactions Redox reactions (oxidation-reduction)

8 EQUATIONS FOR AQUEOUS IONIC REACTIONS Molecular equation: shows all the reactants and products as intact, undissociated compounds (sometimes we will be required to balance the chemical equation first). Ionic equation: shows all the soluble ionic substances dissociated into ions. Net ionic equation: eliminates the spectator ions and shows the actual chemical change that takes place.

9 NET IONIC EQUATIONS Steps: Write the balanced molecular equation - you may have to predict the products of the reaction. Ionize all strong electrolytes in solution. Cancel all spectator ions. Write the leftover species.

10 PRECIPITATION REACTIONS Precipitation reactions occur when pairs of insoluble ions (e.g. Ag + and Cl - ) both present in solution at the same time. A mixture of aqueous solutions may result in more than one precipitate being formed, if more than one insoluble pair is present. Knowledge of the common soluble and insoluble ions is required to predict precipitations (The Solubility Rules).

11 PREDICTING PRECIPITATION 1. Note the ions present in the reactants. 2. Consider the possible cation-anion combination. 3. Decide wether any of the ion combinations is insoluble and thus, form a precipitate.

12 ACIDS AND BASES Acids - produce H + (aq) when dissolved in water Bases - produce OH - (aq) when dissolved in water Strong acid/base - completely dissociates in water Weak acid/base - incompletely dissociates in water

13 ACIDS Monoprotic: one ionizable hydrogen HCl + H2O H3O + + Cl - Diprotic: two ionizable hydrogens H2SO4 + H2O H3O + + HSO4 - HSO4 - + H2O H3O + + SO4 2- Triprotic: three ionizable hydrogens Polyprotic, generic term meaning that there is more than one ionizable hydrogen on the molecule. H3PO4 + H2O H3O + + H2PO4 - H2PO4 - + H2O H3O + + HPO4 2- HPO H2O H3O + + PO4 3-

14 BASES Monobasic: yields one OH - ion KOH K + + OH - NH3 +H2O NH4 + + OH - Dibasic: yields two OH - ions Ba(OH)2 Ba OH - Ca(OH)2 Ca OH -

15 SELECTED ACIDS & BASES Strong Acids Hydrochloric acid, HCl Hydrobromic acid, HBr Hydroiodic acid, HI Nitric acid, HNO3 Sulfuric acid, H2SO4 Perchloric acid, HClO4 Weak Acids Hydrofluoric acid, HF Phosphoric acid, H3PO4 Acetic acid, CH3COOH (or HC2H3O2) Strong Bases Sodium hydroxide, NaOH Potassium hydroxide, KOH Calcium hydroxide, Ca(OH)2 Strontium hydroxide, Sr(OH)2 Barium hydroxide, Ba(OH)2 Weak Bases Ammonia, NH3

16 ACID-BASE NEUTRALIZATION Acid + Base Water + Salt Molecular equation Total ionic equation HCl(aq) + NaOH(aq) H2O(l) + NaCl(aq) H + (aq) + Cl - (aq) + Na + (aq) + OH - (aq) H2O(l) + Na + (aq) + Cl - (aq) Net ionic equation H + (aq) + OH - (aq) H2O(l) Hint: Balance the H + with OH - the rest will work itself out.

17 AN AQUEOUS STRONG ACID-BASE REACTION ON THE ATOMIC SCALE

18 ACID-BASE TITRATION

19 QUESTION What is the concentration of a sulfuric acid solution if it requires ml of a M sodium hydroxide solution to titrate ml of the sulfuric acid solution?

20 QUESTION A ml solution of phosphoric acid is titrated (neutralized) with ml of a M barium hydroxide solution. From this information determine the concentration of the phosphoric acid solution. Does a precipitate form?

21 Insoluble SOLUBILITY RULES 1) All common metal hydroxides are insoluble; except those of Group 1A(1) and the larger members of Group 2A(2) - beginning with Ca 2+. 2) All common carbonates (CO3 2- ), phosphates (PO4 3- ) and chromates (CrO4 2- ) are insoluble; except those from Group 1A(1) and ammonium (NH4 + ). 3) All common sulfides (S 2- ) are insoluble; except those of Groups 1A(1), 2(A)2 and NH4 +.

22 OXIDATION NUMBER RULES General Rules 1. For an atom in its elemental form (e.g. Na, O2, Cl2,...) the O.N. = For a monoatomic ion (e.g. Br -, Cu 2+,...) the O.N. = ion charge. 3. The sum of the O.N. values for atoms in a compound equals zero. For polyatomic ions the sum equals the charge of the ion. Specific Rules 1. For Group 1(A)1 - O.N. is +1 in all compounds 2. For Group 2(A)2 - O.N. is +2 in all compounds 3. For hydrogen - O.N. is +1 when bound to nonmetals 4. For fluorine - O.N. is -1 when bound to metals & boron 5. For oxygen - O.N. is -1 when in peroxides (e.g. H2O2) - O.N. is -2 for all others (except with fluorine) 6. For Group 7(A)17 - O.N. is -1 when with metals, nonmetals (except O) & for other halogens lower in group

23 OXIDATION NUMBERS The main group elements can have different oxidation numbers depending on the molecule they are part of. Compound O.N. of nitrogen NH3-3 N2H4-2 NH2OH -1 N2 0 N2O +1 NO +2 NO NO2 +4 NO3 - +5

24 ASSIGNING OXIDATION NUMBERS (a) H2S (b) SO3 2- (c) Na2SO4 (d) KNO3 (e) AlH3 (f) NH4 + (g) H2PO4 -

25 REDOX REACTIONS

26 REDOX REACTION IN COMPOUND FORMATION Electrons are transferred in the formation of ionic compounds. Electrons are shifted in the formation of covalent compounds.

27 REDOX TERMINOLOGY 2Mg(s) + O2(g) 2MgO(s) 2Mg 2Mg e - O2 + 4e - 2O 2- O.N.: 0 +2 O.N.: 0-2 Mg loses electrons Mg is oxidized Mg is the reducing agent The oxidation number of Mg is increased O gains electrons O is reduced O is the oxidizing agent The oxidation number of O is decreased

28 OXIDATION REDUCTION OIL RIG Oxidation is loss of electrons Reduction is gain of electrons LEO GER Lose electrons is oxidation Gain electrons is reduction

29 QUESTION What is the oxidation number of carbon in Na2C2O4? Oxidation number:

30 QUESTION Identify the oxidizing agent and reducing agent in the following reaction: Sn(s) + 2H + (aq) Sn 2+ (aq) + H2(g) Oxidizing agent Reducing agent Answer H + Sn A H + Sn 2+ B Sn H + C Sn H2 D Sn 2+ H2 E

31 TYPES OF REDOX REACTIONS The different types of redox reactions are classified by the components of the reaction and what happens to those components. There are four types of redox reactions which involve elements - combination, decomposition, displacement and combustion. In these reactions, elements may be reagents, products or transferred during the reaction.

32 COMBINATION REACTION 2K(s) + Cl2(g) 2KCl(s) 2NO(g) + O2(g) 2NO2(g)

33 DECOMPOSITION REACTION 2H2O(l) 2HgO(s) 2Hg(l) + O2(g) electricity 2H2(g) + O2(g) = heat

34 DISPLACEMENT REACTION An active metal displacing hydrogen from water 2Li(s) + 2H2O(l) 2LiOH(aq) + H2(g)

35 DISPLACEMENT REACTIONS Displacing one metal by another metal Cu(s) + 2AgNO3(aq) Cu(NO3)2(aq) + 2Ag(s) Zn(s) + CuSO4(aq) ZnSO4(aq) + Cu(s) More reactive Less reactive

36 COMBUSTION REACTIONS Combustion reactions always involve oxygen. The reactions reduce oxygen and release energy, frequently as heat and light. 2CO(g) + O2(g) 2CO2(g) 2C4H10(g) + 13O2(g) 8CO2(g) + 10H2O(g) C6H12O6(g) + 6O2(g) 6CO2(g) + 6H2O(g)

CHEM 200/202. Professor Gregory P. Holland Office: GMCS-213C. All s are to be sent to:

CHEM 200/202. Professor Gregory P. Holland Office: GMCS-213C. All s are to be sent to: CHEM 200/202 Professor Gregory P. Holland Office: GMCS-213C All emails are to be sent to: chem200@mail.sdsu.edu My office hours will be held in GMCS-212 on Monday from 12:00 pm to 2:00 pm or by appointment.